The present invention relates to a reel-driving clutch assembly for a magnetic recording and reproducing apparatus such as a video cassette tape recorder, and particularly to a reel-driving clutch assembly suitable for adapting a variation of torque in reel tables at the time of Play mode or Rev mode.
In a conventional video cassette tape recorder (hereinafter, referred to as a VCR), a rotary head drum is disposed at the rearward a supply reel and take-up reel, a capstan shaft and a pinch roller driven by the driving force of a capstan motor are mounted at the outlet side of tape on the rotary head drum and also mounted thereat is an audio control head. And at the inlet side of tape on the rotary head drum, a full erasing head, a tension control device for controlling a tension of tape, and a number of slant or vertical guide posts and rotatable guide rollers are respectively mounted.
In such a construction, since a tape travels with contacting the parts of the tape running system a load is generated in the tape due to the friction therebetween, and the tape in running toward the take-up reel or the supply reel has different loads each other depending upon the condition of installation of the parts.
Furthermore, since the various parts are disposed on a base plate of a deck dependently upon play mode, the larger power is required when the tape is wound up on the supply reel than when the tape is wound up on the take-up reel, as a result a higher torque is required on the supply reel at the time of Rev mode than the wound up torque required on the take-up reel at the time of play mode.
In a 1/2 inch VHS-type VCR, for example, the take-up reel needs a torque of about 150 g. cm in play mode, and the supply reel needs a torque of about 190 g. cm in Rev mode. Such difference of torques between the supply reel and the take-up reel are adapted not only to a VHS-type VCR but also to the majority of VCR having a contruction provided with a supply reel and take-up reel.
Therefore, a separate device is required for the purpose of making a torque of the supply reel large more than that of the take-up reel in a VCR.
Such a device is illustrated in FIG. 1, in which a take-up clutch gear 31 and a supply clutch gear 32 both having different clutch forces are respectively disposed and an idler gear 34 is also disposed in such a manner that it can transmit a driving force selectively to a supply reel 35 or a take-up reel 36 therebetween. And, in a type that a clutch gear is disposed between a supply reel 35 and a take-up reel 36 so that the supply reel 35 or the take-up reel 36 can be selectively driven by making use of a belt pulley 33, a reel-driving device, which can vary the torques of Play mode and Rev mode by making the diameter of the supply reel 35 is larger than that of the take-up reel 36, is also known.
In the conventional device as shown in FIG. 1, when a belt pulley 33 and a gear 33' rotates in the counterclockwise by the driving force of a capstan motor (not shown) via a belt 37 at the time of Rev mode, an idler gear 38 meshed with the gear 33' is rotated in the clockwise and an idler gear 34 connected with a lever 39 is swung in the counterclockwise centering around a shaft 40 so that it can mesh with a supply clutch gear 32, thereby a clutch force is transmitted to a supply reel 35 to generate the torque of Rev mode.
And, at the time of Play or Rev mode, the capstan shaft rotates in the reverse direction in contrast with the above so that the idler gear 34, is meshed with the take-up clutch gear 31, thereby a clutch force is transmitted to the take-up reel 36 to generate the torque of Play mode.
However, in such a conventional device, there has been some drawbacks in that since the respective clutches are necessary for the supply reel and the take-up reel in order to vary the torques between Rev mode and Play mode, thus giving rise to increasement of the cost due to its complicated structure.